Bleaching process.



PATENTED DEC. 15, 1903.

M. RUTHENBURG. BLEAGH-ING PROCESS.

APPLICATION HLED FEB. 14. 1902.

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BLEACHING PROCESS.

SPECIFICATION forming part of Letters Patent No. 747,234, dated December 15, 1903.

Application led February 14. 1902. Serial No. 94.084. (No specimens.)

.To @Z whom it may concern.:

Be it known that I, MARCUS RUTHENBURG, of Harrisburg, in the State of Pennsylvania, have invented certain new and useful Improvements in Bleaching Processes, whereof the following is a specification, reference being had to the accompanying drawings.

My invention relates to processes for bleaching stuff, such as paper-pulp and the like, electrolytically; and it is the object of my invention to obtain the maximum bleaching effect from a given quantity of chemical and electric current employed.

It is characteristic of my 'process that the stuff to be bleached is intimately mixed with an aqueous solution comprising a chemical which is subsequently decomposed to form a bleaching agent while in said stuff. A

In the conduct of my process I have found it convenient to employ an aqueous solution comprising twenty per cent. of sodium chlorid and to mix said solution with the stuff to be bleached in such proportion as to not only thoroughly impregnate the particles of the stuff with the chemical to be decomposed, but to render the mixture of such consistency as to be readily progressed between the electrodes. I have also found it advantageous to mix with said solution of sodium chlorid an aqueous solution containing ten per cent. of hydrated oxid of calcium, the effect of such addition being that any chlorin liberated from the sodium chlorid is taken up by the hydrated oxid of calcium, forming additional soluble chlorin salt in the mixture, with augmented bleaching effect. Although I prefer to employ the oxid of calcium because of its low cost, it is to be noted that an equivalent eifectmay be produced in the mixture by the addition of the oxid of any of the earth metals, such as magnesium, lithium, aluminium, sodium, and potassium.

I have obtained satisfactory results by exposing the saturated stuff for approximately five minutes between electrodes supplied with electric current in the proportion of one-half ampere per square inch of the electrode surface exposed to the mixture and at a pressure of three volts. It is to be understood, however, that the desired electrolysis of the mixture may be eftectedoy more or less exposure to an electric current of dimensions differing from those above specified. It is also to be noted that the aforesaid addition of oxd of calcium to the mixture increases the conductivity of the latter, and thus effects a considerable saving in the amount of the electric current employed to effect the electrolysis.

In the drawings, Figure I is a central vertical sectional view of an apparatus conveniently adapted for the conduct of my process. Fig. II is a longitudinal sectional view of said apparatus,taken on theline II IIin Figi.'

In said figures, l is the casing, provided with a suitable inlet 2 and outlet 3, through which the mixture 4 of saturated stuff is progressed by any convenient means-for instance, said casing may be connected with a pump or may be vertically disposed, so that the mixture 4 gravitates therethrough. Said casing lis provided with lids 6,which are conveniently removable and serve as supports for the electrodes 7. The plates 8 being alternately disposed between said electrodes 7,the mixture 4. is caused to traverse the entire surface of said electrodes in its progression between them. Said plates 8 may be electrodes similar to the electrodes 7 The electrodes 7 at the opposite extremities of the series mounted in said casing l being connected by the conductors 9 with the source of electric current l0, the saturated stuff 4 is so agitated by its progression through the casing l between the electrodes that the particles of material to be bleached are successively exposed to the surface of said electrodes and subjected to the action of the current passing between them.

I am aware that it has been hitherto known that a bleaching agent may be produced by electrolyzing a solution of sodium chlorid, but so far as I am aware such electrolysis as has been effected in the prior art has been aside from and independent of the stuff which is to be bleached. My present process is advantageous in that the electrolytic decomposition of the chemical to form the bleaching agent is not effected until it is actually within the substance to be bleached, and the bleaching agent thus produced is characterized by greater bleaching efficiency than a bleaching agent of equal oxidizing capacity which is produced aside from the stulif to be bleached and subsequently applied thereto.

IOO

The effect of the bleaching agent is not only more rapid when produced under the conditions characteristic of my process, but for a given degree of whiteness obtained there is `less detraction from the weight of the material treated.

I find that some grades of commercial sodium chlorid contain impurities which it is desirable to eliminate before mixing the solution with the stuff to be bleached. Therefore I find it convenient to purify such sodium chlorid by subjecting it to the action of an electric current of low Voltage while in saturated aqueous solution, with the result that said impurities are oxidized and may be removed by'a filter.

No portion of the chemical employed in my process need be wasted, as sodium sulfite may be produced from the residue of the bleaching solution after its removal from the bleached stuff by the addition of SO2. Although I have described a particular type of apparatus as means by which my process may be conducted, I do not desire to limit myself thereto, as it is obvious that other forms of apparatus may be devised for the purpose described. Moreover, in view of the variable nature of the chemicals named I do not desire to limit myself to the particular percentages thereof above specified.

I claim- 1. The hereinbefore-described bleaching process, which consists in intimately1 mixing, with the stuff to be bleached, a chemicallyneutral aqueous solution; progressing the saturated stuft' between opposed plates arranged in series and, maintaining said plates energized solely through said stuff, so that the solution is decomposed in said stu and the latter bleached during its progression between said plates, substantially as set forth.

2. The hereinbefore-described bleaching process, which consists in intimately mixing,- with the stuif to be bleached, an aqueous solution, comprising sodium chlorid and hydrated oxid of calcium; progressing the saturated stuff between opposed plates arranged in series; and, maintaining said plates energized solely through said stu, so that the solution is decomposed in said stuff and the latter bleached during its progression between said plates, substantially as set forth.

3. The hereinbefore-described bleaching process, which consists in intimately mixing, with the stuff to be bleached, a chemicallyneutral aqueous solution; progressing the saturated stuff between opposed plates arranged in series whose alternate members are respectively active and neutral, and, maintaining said active plates energized solely through said stuff, so that the solution is decomposed in said stuff and the latter bleached during its progression between said plates, substantially asset forth.

In testimony whereof` I have hereunto signed my name, at Harrisburg, Pennsylvania, this 12th day of February, 1902.

MARCUS RUTHENBURG.

Witnesses:

D. AsHMoRE CALEY, WM. H. EARNEST. 

